(1) Field of the Invention
The invention relates to a method of metallization in the fabrication of integrated circuits, and more particularly, to a method of cleaning the contact hole before metallization in the manufacture of integrated circuits.
(2) Description of the Prior Art
In a common application for integrated circuit fabrication, a contact/via opening is etched through an insulating layer to an underlying conductive area to which electrical contact is to be made. A barrier layer, typically titanium nitride, is formed within the contact/via opening. A conducting layer material, typically tungsten, is deposited within the contact/via opening. As device sizes continue to shrink, these typical materials are no longer adequate. Because of its lower bulk resistivity, Copper (Cu) metallization is the future technology for feature sizes in the deep sub-half-micron regime. Cu has been used successfully as an interconnection line. The damascene or dual damascene process has become a future trend especially on the copper metallization process because of the difficulty in metal etching. These processes are discussed in ULSI Technology, by Chang and Sze, The McGraw Hill Companies, Inc., NY, N.Y., c. 1996, pp. 444-445. When a connection is to be made to an underlying copper interconnection line, the copper exposed within the contact opening easily oxidizes. It is necessary to remove this copper oxide as well as polymer residues from the contact opening before metallization.
U.S. Pat. No. 5,200,360 to Bradbury et al teaches an Ar sputter etch for one minute to remove inorganic material from the bottom of a contact opening and an oxygen plasma descum for 15 seconds to remove polymer residue. U.S. Pat. No. 5,460,689 to Raaijmakers et al teaches an Ar sputter etch at high and low pressure wherein the corners of the contact opening are rounded. U.S. Pat. No. 5,670,421 to Nishitani et al teaches Ar sputtering and a Cl.sub.2 plasma or N.sub.2 treatment. U.S. Pat. No. 5,736,458 to Teng teaches an Ar sputter clean, barrier layer deposition, and then an N.sub.2 treatment before metal deposition.